The development of antibiotic resistance has become a serious problem in medical microbiology. Newer generation .beta.-lactam antibiotics such as methicillin were developed largely to overcome the resistance to earlier developed types of penicillins; such resistance has spread rapidly among pathogenic bacteria. However, methicillin resistant bacterial strains are now frequently encountered, notably among the Staphylococci.
Non-.beta.-lactam antibiotics are often used for treating particular types of infection. Polymyxins are often used for treating skin infections due to gram-negative bacteria, such as Pseudomonas. However, the toxicity of these compounds restricts their parenteral use, and these compounds usually are administered topically in ointments. Polymyxins are not known to be effective against microorganisms other than gram-negative bacteria.
Fungal infections generally are treated with quite different types of antibiotics. Notably, topical Candida infections usually are treated with imidazole derivatives (e.g., clotrimazole) or nystatin.